1. Field of the Invention
This invention relates generally to improvements in static structural elements and especially to precast composite building modules and to the method of their manufacture.
In particular, the construction panel of this invention concerns preformed concrete sandwich panels which bond dissimilar construction materials to form lightweight, load bearing units having acoustical and thermal insulating properties.
The process for forming the composite construction panel of this invention further involves a continuous molding operation with provisions for incorporation of electrical conduit and access openings.
2. Description of the Prior Art
The development of lightweight precast construction panels has been gradual and not without many shortcomings. Initial attempts to reduce the weight of concrete structural elements included the introduction of filler additives to the aggregate. This, however, was detrimental to the strength and durability characteristics of the concrete. Another technique for bonding lightweight materials with concrete utilized a plurality of laminations having interconnecting dowels such as described in U.S. Pat. No. 3,295,278. The effectiveness of that bond method and the availability of different panel shapes and sizes were, however, severely limited. A further system of adhering concrete to a plastic foam layer was noted in U.S. Pat. No. 4,010,232 wherein a flowable foam mixture was poured upon a blanket of powdered dry cement. The so formed slab did not comprise a complete encasement of the foam material, and it was questionable whether that system did in effect produce a unitary structure.
A further attempt to overcome the problem of accomplishing a composite structure employed precast concrete shells into which a flowable foam composition was placed. The module formed by this procedure differed substantially from the prefabrication process and product of the instant invention. The present invention requires no premolding of relatively fragile or brittle glass fiber reinforced concrete shell components as in the method described in U.S. Pat. No. 3,984,957, and consequently the thickness of the glass fiber reinforced layers can be designed to meet the loading requirements of the building panel without any additional loads being taken into consideration for fabrication purposes.
In contrast to the previously described structures and methods of fabrication, this invention provides an improved process for forming a composite construction panel which overcomes many of the noted disadvantages.
It will be apparent that the method of this invention provides for an improved bonding of a plastic foam core within reinforced concrete encasement in a manner having distinct advantages over the prior art.